Process for oxidizing olefins to aldehydes and ketones



United States Patent 3,118,001 PRUCEdS FGR OXKDHZHNG OLEFINS T0 W wALDEHYDES AND KETQNES Wilhelm Riemenachneider, Franliturt am Main,Germany,

designer to Farbwerke Hoeehst Aktiengesellschait vorrnals Meister Luciusdz Brilning, Frankfurt am Main, Germany, a corporation of Germany NoDrawing. Filed Jan. 23, 1959, Ser. No. 788,488 Claims priority,application Germany Jan. 28, 1958 5 flaims. (Cl. 260-586) The presentinvention relates to a process for oxidizing olefins to aldehydes,ketones and acids.

It has already been proposed to oxidize ethylene catalytically by meansof an argentiferous catalyst to ethylene oxide, or by means of anoxidation catalyst other than u silver-containing catalyst at a raisedtemperature to obtain mixtures of formaldehyde, acetaldehyde, formicacid, acetic acid and other products. In these processes, however,acetaldehyde or acetic acid cannot be produced in a. yield interestingfrom an economical point of view. Our experiments have revealed that theoxidation carried out under such conditions in the presence of a noblemetal catalyst likewise involves small yields of acetaldehyde, and therelative proportion of formaldehyde obtained generally preponderates.

It is also known that compounds of palladium, platinum, silver, orcopper form complex compounds with ethylene. Furthermore, the formationof acetaldehyde was observed in decomposing a potassium-platinum-complexcompound. Other unsaturated compounds may favor the complex formation.In this case stoichiometric reactions are concerned yielding the noblemetal as such.

It has also been described to reduce palladous chloride by means ofethylene in the presence of water to palladium metal. In this reductionthe formation of acetaldehyde was observed. It is also known thatpalladous chloride dissolved in water can be reduced rapidly andcompletely to palladium by means of propylene, even if propylene isadmixed with nitrogen or air, or by means of isobutylene. It isdescribed that carbon dioxide is not evolved in any one of the aforesaidreductions.

In a number of prior applications various processes are describedaccording to which carbonyl compounds can be obtained from thecorresponding olefins in a good yield and, if desired, in a continuousmanner by contacting said olefins with an oxidizing agent, a liquidcatalyst having an acid to neutral reaction and comprising water, acompound of the noble metals belonging to group VIII of the periodictable and a redox system. In this connection reference is made to thefollowing applications, all relating to a Process for oxidizing olefinsto aldehydes, ketones and acids:

Serial No. 747,116, filed July 8, 1958, by W. Berndt, L. Hdrnig, U.Schwenk, W. Riemenschneider, W. Schmidt and O. E. Blinder, Serial No.750,150, filed July 22, 1958, Serial No. 763,691, filed September 26,1958 and now abandoned, Serial No. 768,624, filed October 21, 1958,Serial No. 770,007, filed October 28, 1958, now Patent No. 3,076,032,Serial No. 769,912, filed October 27, 1958, Serial No. 769,554, filedOctober 27, 1958.

In the aforesaid applications the term carbonyl compounds is used in itsbroad sense, i.e. it covers not only aldehydes and ketones but alsocarboxylic acids such as acetic acid.

It is supposed that in the reaction described in the aforementionedapplications the oxidation of the redox system added, i.e. for examplethe oxidation of intermcdiately formed cuprous chloride to cupricchloride, is the velocity determining step for the entire reaction.Since it is advantageous to accelerate a slow reaction in order toarrive at a high conversion, care must be taken that the redox systemundergoes rapid oxidation by the "ice oxidizing medium, such as oxygenor gases containing oxygen, preferably air. Oxidation may be acceleratedby a fine distribution of the oxidizing gases or by operating under araised partial pressure of oxygen, or by addition of an inorganicoxidation promoter.

It has been stated in the aforesaid applications that sometimes thepresence of a salt, such as sodium chloride or potassium chloride, mayprove advantageous. For example, these salts-like hydrochloric aciditself or other alkali metal or alkaline earth metal halides such asLiCl, CaCl MgCl or other salts such as FeCl FeCl ZnCl or CuCl -improvethe solubility of CuCl, which may be formed in the course of thereaction and is only very sparingly soluble in water (0.11% at C.).solubility of CuCl may also be improved by addition of formic acid.However, the use of these additives for improving the solubility ofcuprous chloride has the disadvantage that relatively large amountsthereof are necessary. Accordingly a relatively concentrated solution isformed in which the solubility of oxygen is decreased compared with morediluted solutions. This means that by the application of such additivesan increased concentration of one reactant (the cuprous ion) can only beattained by a decrease of the concentration of the other reactant (theoxygen).

I have now found that the aforesaid disadvantages can be avoided ifhalogenated acetic acids or salts thereof are used as dissolvingintermediaries in catalysts containing as essential ingredient copperchloride. In these catalysts cuprous chloride is formed during thereaction which is regenerated to yield cupric chloride by the action ofthe oxidizing agent. The halogenated acetic acids or the salts thereofhave a very strong dissolving action on CuCl and therefore they needonly be added in a minor amount, generally 150%, by weight calculatedupon the amount of copper (CuCl lfi O) contained in the solution. Thereduction of the oxygen solubility in the contact liquid, which isotherwise caused by the presence of the required large amounts offurther additives, is therefore only small. Adding halogeno-acetic acidor a salt thereof is especially advantageous in view of the fact thatthese compounds prevent CuCl from being precipitated during thereaction. Since precipitated CuCl would be no longer available for thereaction and might cause clogging and other difficulties, a reduction inthe yield and disturbances are prevented. In view of the fact that CuClis kept in solution there always appears a high concentration of cuprousions which are available for a reaction with the more or less greatamount of oxygen present. This favors the desired rapid oxidation to thereadily soluble CuCl which is presumably the velocity-determining stepfor the entire reactionand accelerates the entire reaction.

From among the halogenated acetic acids trichloro acetic acid and alsodibromoacetic acid are especially active. The solubility of CuCl in 2.5%aqueous trichloroacetic acid, for example, is more than 50 times thesolubility of CuCl in water.

Salts of halogenoacetic acids, mixtures of these salts, or mixtures ofthese salts with free halogenoacetic acids, may also be used with asimilar result. As salts there may be used those with inorganic cationsor with organic bases. There may be mentioned more especially, salts ofalkali metals, ammonia, alkaline earth metals, for example of sodium,potassium, lithium, magnesium, calcium, barium, iron, copper, palladium,or cerium, and also salts of triethylamine, tripropylamine, diand/ortriethanolamine.

Substituting the aforesaid salts for the free halogenoacetic acidsinvolves the advantage that too strong an acidification and accordinglya decrease in conversion are avoided. The optimum amount of salts to beadded is dependent on the composition of the catalyst used in each Theindividual case. When a contact is concerned containing, per liter ofwater, lOO grams of CuCl .2H O and 2 grams of PdCl it suifices to add25% of trichloroacetic acid or the corresponding amount of salts, thepercentage figures being calculated upon the amount of copper, which inturn is calculated as CuCI Q I O. The addition of the aforesaidsubstances in preparing carbonyl compounds from olefins involves asmooth reaction and an increased conversion.

The process of the present invention may be carried out with thecatalysts and under the conditions broadly described in tieabove-mentioned applications, or preparing carbonyl compounds from thecorresponding olefins, i.e. olefins having the same number of carbonatoms as the carbonyl compounds. These catalysts contain a compound of anoble metal of group Vlli of the periodic table, particularly palladium,and a chloride of copper and, if desired, one or more redox systems.

As redox systems there may be present, for example, those that containin addition to the chloride of copper, compounds of metals which underthe reaction conditions employed may appear in various oxidation stages,for example compounds of mercury, cerium, thallium, tin, lead, titanium,vanadium, antimony, chromium, molybdenum, uranium, manganese, iron,cobalt, nickel or osmium, and also inorganic redox systems other thanthe latter, preferably in admixture with compounds of other of theaforesaid metals specified above, such as sulfite/sulfate, orarsenite/arsenate systems and/or organic rcdox systems, for exampleazobenzene/hydrazobenzene, or quinones or hydroquinones of the benzene-,anthraceneor phenanthrene series.

As compounds of the noble metals of group VIII of the periodic tablethere may be used in the process according to the present invention, forexample, compounds of palladium, iridium, ruthenium, rhodium, orplatinum, i.e. of metals the stable valence of which is at most 4.Compounds of this series of metals are believed to be capable of formingaddition compounds or complex compounds with ethylene. The reaction maylikewise be carried out in the presence of a noble metal from which, inthe course of the reaction, the reactive compounds are formed.

As oxidizing agent there may be used, for example, oxygen, if desired inadmixture with an inert gas. The oxygen may be employed, for example, inthe form of air, which is the cheapest oxidizing agent, or in the formof air enriched with oxygen. The use of air is, however, confined tocertain limits, it the unreacted gases are circulated, inasmuch asnitrogen concentrates as ballast material.

The reaction may be supported or carried out by addition or" an activeoxidizer, which are broadly listed in the above mentioned applications.

It is often advantageous to add, prior to or dining the reaction, acompound yielding anions under the reaction conditions applied, forexample an inorganic acid, preferably a mineral acid, such as sulfuricacid, nitric acid or a volatile acid, such as hydrochloric acid orhydrobromic acid, or a salt such as ammonium chloride, ammonium bromide,zinc chloride, aluminum chloride, iron chloride, chromic chloride,titanium tetrachloride, sodium hydrosulfate, a halogen such as chlorine,bromine, or bromotrichloride, or a halogen-oxygen compound, for examplehypochlorous acid, brornic acid, chlorine dioxide, or thionyl orsulfuryl chloride, or also an organic substance, preferably a saturatedaliphatic halogen compound of low molecular weight such as ethylchloride, propyl chloride, butyl chloride, acetyl chloride, benzoylchloride, propionyl chloride, phosgene. Such addition enables a possibledecrease of anions to be counteracted and the lifetime of the catalystto be prolonged.

The process of the present invention is carried out in solution atrelatively low temperatures. Preferably a pure aqueous solution is used,but the reaction may like- Cir 4 Wise be carried out in aqueoussolutions in which the water is diluted with a hydrophilic solvent, suchas acetic acid, acetone, methylethylketone or other ketoncs, ethyleneglycol, propylene glycol, glycerol, dioxane or mixtures thereof.

The present process is carried out with special advanrage attemperatures within the range between 50 and 160 C., preferably 50 and(3., since it is carried out in the liquid phase, it is necessary tooperate under a raised pressure it the temperature used is above theboiling point of the catalyst solution. If desired, the process may alsobe carried out at temperatures outside the ranges indicated above, forexample at 170 C. to 18' C., or for example at 40 C., or within a rangeof, for example, 80 C. to C. Furthermore atmospheric pressure, a raisedpressure or reduced pressure may be applied, that is, a pressure of upto 100, preferably of up to 50 atmospheres gauge. The process may becarried out under pressure regardless of whether the temperatures usedare above or below 108 C. it is furthermore of importance to carry outthe process in an acid to neutral medium. The preferred pl-l-values arewithin the range between 0.8 and 3; higher pl-l-values between, forexample, 0.8 and 5 or 2 and 6, or lower plivalues, for example 0.5, mayalso be used, although such pH-values generally do not involve a specialadvantage.

In addition to the use of halogenated acetic acids or the salts thereofit is possible to influence the solubility of cuprous chloride to acertain extent by modifying the ratio of olefin to oxygen. The moment atwhich the olefin to oxygen ratio is modified, can be readily determinedby continuously measuring the pH, which may be performed by any knownmethod.

If the pH decreases, it is easily possible to readjust the optimumpH-range by adding either more oxygen or less olefin, or by combiningthese two steps. If the pH increases, the optimum pH-range can bereadjusted inversely. This method of controlling the reaction may alsobe combined with the above described addition of compounds yieldinganions.

Sometimes it may be advisable to provide the pH- measuring device withan automatic connection to the dosing device for the supply of ethyleneand oxygen. in this case the pH is once adjusted to the optimum valueand the reaction can then be controlled automatically.

In the process of the invention likewise sometimes the presence of asalt, such as sodium chloride or potassium chloride or other saltsmentioned above, may prove advantageous.

The reaction may be supported by increasing the ethylene and/or oxygenconcentration in the reaction space, for example, by increasing thepressure and/ or by the presence of a solvent. The ethyleneconcentration in the reaction solution may be considerably increased,for example by using higher concentrations of metal salts bindingethylene, for instance copper-, iron-, mercuryor iridium-compounds,especially halides, or the sulfates, the latter especially when mercuryis concerned, or by using organic solvents which are preferably misciblewith water, for example acetic acid, methylethyllaetone or otherlretones, monoor polyhydric alcohols, acyclic ethers or dimethylformamide. The gases may be circulated, if desired, for example a gascontaining a to percent of unreacted oxygen.

Due to the presence of oxidizing agents acetic acid may be formed in asmall amount in addition to acetaldehyde. If desired, the oxidation ofacetaldehyde to acetic acid which is known in the art, may be combinedwith the reaction described above in order to omit partially or totallythe aldehyde stage, or acetaldehyde may be oxidized in a second stage inknown manner to acetic acid, for example in the presence om manganesecompounds.

Under the conditions specified above under which ethylene yieldsacetaldehyde, propylene yields preponderantly acetone andpropionaldehyde. ocand fi-butylene yield preponderantlymethylethylketone, the ot-butylene yielding also butyraldehyde, andisobutyraldehyde can be obtained from isobutylene.

In the case where higher olefins are concerned, such as pentene and itshomologs, cyclohexene or styrene, the reaction proceeds substantially ina manner analogous to that described and it can be carried out under thesame conditions as set forth above. Due to the relatively mild reactionconditions there are almost exclusively obtained those oxidationproducts which had to be expected in view of their structure, withoutnoteworthy isomerizations or molecule decompositions occurring.

Mixtures of olefins or gases containing olefins or other unsaturatedcompounds may be reacted in the same manner, provided they are capableof reacting under the reaction conditions, for example diolefins. Thereaction of olefins containing 2 to 3 carbon atoms is, however,preferred. Under circumstances, the reaction conditions must be adaptedto the compounds used and to their physical properties. The higherboiling points of the reaction products may also required acorresponding modification of the reaction conditions. Diacetyl may beobtained, for example, from butadiene.

The reactants may be diluted by gases inert towards the reaction, forexample by nitrogen, carbon dioxide, methane, ethane, propane, butane,isobutane and other saturated aliphatic compounds and furthermore byother compounds such as cyclohexane, benzene or toluene.

The olefins may, however, not only be diluted by one or more of theaforementioned gases, but likewise with carbon monoxide and/ orhydrogen, if desired in addition to the aforementioned gases, andincreased pressure may be applied. If such gas mixture contains CO,oxygen should be present at least in an amount as is necessary toconvert the olefin to aldehyde and carbon monoxide to carbon dioxide.From a mixture of carbon monoxide and. olefin, practically the sameamounts of carbonyl compounds are obtained as if no carbon monoxide werepresent. In this reaction the carbon monoxide is partially converted tocarbon dioxide.

If hydrogen is present, the major amount of hydrogen remains unaltered,whereas a small portion thereof reacts with formation of water andanother small portion with hydrogenation of the olefins. The fact thatneither hydrogen nor carbon monoxide affect the process of the inventionis of special advantage since accordingly industrial gases, for examplerefined gases or gases obtained in cracking processes, may be used asstarting materials. All expensive gas separations can therefore bedispensed with, although a prepurification or concentration of theolefin may prove advantageous. Carbon monoxide and/ or hydrogen mayappear in the gas mixture, for example in double the amount of theolefin, and yet the olefin oxidation is not substantially impaired. Thisstatement is, however, not intended to indicate a limit. If these gasesare present, the multiple stage process which is sometimes very suitablefor the present reactions and which is described in application Ser. No.750,150, may be applied with special advantage. In this process theolefin, if desired in admixture with a small amount of oxygen, iscontacted with the catalyst in one stage, while the oxidizing agent iscontacted with the catalyst in a second stage or apparatus. As a resultof these measures it is possible to practically avoid a mixing of thegases used with oxygen, so that the former can be used for furtherpurposes after having left the reactor.

For stoichiometric reasons the molar ratio of olefin to oxygen must be2:1 in the complete oxidation of the olefins to the correspondingaldehydes or ketones. To prevent explosions, it is, however, preferredto use an oxygen deficiency, for example in the range of 2.5:1 to 4:1.Still further it is preferred to work outside the range of explosivity,for example with a content of oxygen of 23-20%, or 8-14% under pressure,and to circulate unreacted gas which consists substantially ofnon-converted olefin, if desired in admixture with other inert gases,such as nitrogen and/or with hydrogen and/or carbon monoxide, and whichmay furthermore contain some oxygen. To this gas oxygen and the olefinsuch as ethylene are added as they are consumed.

The present process may be carried out for example by contacting theolefin and oxygen or air simultaneously with the catalytic substances.However, it is often very advantageous to contact the olefin and theoxidizing agent separately with the liquid catalyst used as is describedabove. This latter mode of operating has the advantage, that thecompositions of the gas mixture need not be controlled carefully andthat even in recirculating the olefin, such as ethylene, air may be usedas oxidizing medium without disadvantages being involved.

The regeneration may be brought about by contacting the catalyst withthe oxidizing medium, for example oxygen or air, in an amount sumcientto bring about regeneration under known conditions, for example at 50-C., and, if desired, under pressures and at temperatures being differentfrom those of the first stage in which the catalyst is contacted withthe olefin.

In a frequently useful technical variant of the process of thisinvention, the desired reaction product, for example acetaldehyde, isseparated from the reaction gas, the residual gas which may stillcontain inert gas and/ or hydrogen and/ or carbon monoxide and may befree from oxygen but may likewise contain oxygen, is reintroduced intothe reactor, suitably into its lower part, and an amount of olefin and,if desired, oxygen corresponding to that consumed during the reaction isintroduced into the reactor or the olefin and/or the oxygen are added tothe recirculated gas. For the sake of security the oxidizing agent, i.e.preferably oxygen, if desired in admixture with inert gases, such aspresent in air, is preferably introduced through separate inlets,especially when about stoichiometric amounts of the reactants areapplied and no diluting gas is present.

The oxidizing agent is preferably introduced into the circulationconduit of the catalyst. The amount ot oxygen introduced may be somodified that even in the catalyst solution the explosivity limit isnowhere surpassed. Such modification is generally not necessary; it israther suificient to add the oxygen to the residual gas which escapesfrom the contact solution, in an amount to keep the composition of thisresidual gas outside the explosive limits.

In order to obtain especially high space-time-yields, it is alsopossible to introduce either olefin or oxidizing agent, preferablyoxygen, or olefin and oxygen into the reactor at various places arrangedone above the other or one behind the other. Preferably the inlets foreach reactant are locally separated from the other inlets for the samereactant. It is likewise possible that the amount of oxygen introducedis measured so as to be at all places of the reaction vessel below thelower limits of the explosive range.

In many cases the reaction proceeds likewise smoothly if the catalystsused contain only a small amount of compounds of the noble metalsbelonging to group VIII of the periodic table. In most cases it issutficient to use a catalyst in which the ratio or" the sum of the redoxmetals, especially the sum of copper and iron, to the noble metal,especially palladium, is at least 15:1, preferably 25-500:1. It is,however, preferred to use a catalyst containing copper salts, in whichthe ratio of copper to palladium is above 10:1, for example above 15:1and preferably 50:1 to 500:1, or even above these ranges. This method ofoperating is more economic in view of the fact that the expensivepalladium salt need only be used in a minor amount; it can be used forconverting ethylene and olefins other than ethylene, and may be combinedas desired with variants hereinbefore or hereinafter described. Thisembodiment may also be carried out under elevated pressure.

The reaction of the present invention is favorably inilucnced byirradiation with rays rich in energy, especially in case where oxygen isused as oxidizing medium. Preferably ultraviolet light is applied,conveniently by using a mercury quartz lamp. Such radiation, which mayalso comprise X-rays, activates especially the oxygen, increases itsoxidizing activity, and promotes both the reaction with the olefin and apossible oxidative destruction of by-products, for example oxalic acid.These measures increase tie conversion, reduce the formation ofby-products and considerably prolong the lifetime of the catalyst, theactivity of which may subside after a prolonged time.

If mainly aldehydes and ketones are to be prepared it is advantageous toadditionally prevent or remove an accumulation of carboxylic acids, forexample acetic acid, in the reaction space. This aim may for example beattained by distillation or other means. It is to be noted that theliquid catalysts used in the present reaction may become deplete ofhalogen in the course of time due to the formation of volatilehalogenated by-products, for example methyl chloride or ethyl chloride.For some other reasons it has likewise proved to be advisable in somecases, to keep the molar ratio of copper:halogen and more especially ofcopper:chlorine with the limits of 1:1 and 1:2, preferably Within thelimits of 1:1.4 and 1:1.8. The above ratio of copper to halogen shouldbe understood to irclude the amount of halogen added in the form of ironhalide or another halide of cations which do not form neutral reactingsalts with hydrohalic acids. The amount of halogen which is present inthe form of a neutral salt, for example sodium chloride or potassiumchloride, or is capable of being bound to form a neutral salt, need notbe considered. For example, if the catalyst contains 3 gram equivalentsof alkali metal salts or alkaline earth metal salts of acids other thanhydrohalic acids, 5 gram equivalents (mols) of chlorine ions added inthe form of iron chloride, and 1 mol of copper ions added in the form ofcopper acetate, the copper to chlorine ratio is 1:2 according to thedefinition given above.

The copper to halogen ratio may be regulated by supplying hydrogenhalide, especially hydrogen chloride, and/0r free halogen or compoundsyielding halogen ions under the reaction conditions, such ashalogeno-oxygen compounds or organic substances, for example thosementioned above as compounds for supplying anions.

Sometimes it is advantageous to add to the catalyst a quinonc which maybe substituted by sulfonic acid and/ or carboxyl groups. By such anaddition the reaction velocity and olefin conversion orif the rate ofconversion remains the same-the throughput is considerably increased. Itis supposed that by an addition of the aforesaid compounds the slowestreaction which is the velocity determining step for the entire reaction,e.g. the oxidation of intermediately formed cuprous chloride to cupricchloride is likewise accelerated.

As quinones there may be used, for example, orthoand/or paraquinones,such as benzoquinones, naphtho- 'nones, anthraquinones,phenanthrenequinones, or alkyl substitution products of such quinones orthe substitution products thereof, which have been referred to above. Byadding, for example, the potassium salt of 1.2-naphthoquinonel-sulionicacid to a dilute copper chloride catalyst activated with palladiumchloride, the converon is more than doubled as compared with a catalystree from such addition.

A number of suitable quinones is listed in application Ser. No. 769,554,referred to above.

The quinones or their sulfonic or carboxylic acids or he water-solublesalts of quinone sulfonic acids or quinone carboxylic acids arepreferably used in a proportion of up to percent by weight, calculatedupon the amount of catalyst, and more preferably in a proportion ofbetween 0.1 and 3% by weight.

The conversion and the sp'a'ce time-yield of the present reactiondepend, for example, on the fine distribution of the gas, on theresidence time in the apparatus and the composition of the catalyst, thetemperature and the pressure used. The optimum residence time canreadily be determined by those skilled in the art.

In the process of this invention care should be taken that the heatevolved during the process (high heat effect: about 60 kcal per mol ofaldehyde) is dissipated to the exterior.

The present reaction may be carried out, for example, in verticallyarranged reactors, such as tubes provided with frits or oscillatoryagitators or other usual reaction towers, for example wash towers,suitably filled with filling material. The reaction may likewise becarried out in reactors which are provided at the head with calming orsedative zones in which foamy portions are separated into the liquid andthe gaseous components, and from which the catalyst liquid isreintroduced at the foot of the reactor. Furthermore it is possible tocarry out the reaction in a tube through which the contact liquid andthe reaction mixture flow at a high velocity. The two lastmentionedembodiments may likewise be carried out in two stages as it is indicatedabove.

The gases may be atomized, for example through a frit, or in anothersuitable manner, and too voluminous gas bubbles may be divided intosmaller ones, for example by means of an agitator. For this purposethere may also be used a vibro-mixer or a turbo-mixer. All thesevariants enable the reaction to be carried out continuously.

Condensates which separate from the reacted gas, especially aqueouscondensates, may be recirculated.

It is not necessary that the catalysts used are made of fine chemicals;they may likewise be produced from suitable metals of commercial purity.

As anion the catalyst may contain chlorine ions or halogen ions otherthan chlorine, such as bromine ions, nitrates or chlorateor perchlorateradicals or mixtures of these anions, for example, with sulfate oracetate radicals. Sometimes it is specially advantageous to use acatalyst which contains perchlorate ions.

The apparatus used in the process of this invention should be made of amaterial which is not corroded by the catalyst and preferably has asufilcient thermal con ductivity. Since the catalysts used contain noblemetal compounds, for example palladium compounds, it is less suitable touse the usual metals and alloys as construction material, since there isthe risk and that these less noble metals, in the presence of water andat the indicated temperatures, precipitate the noble metal salt used inthe catalyst, and that they themselves are converted into salt form.

In order to avoid corrosion in the apparatus used, it is often suitableto use an apparatus lined with titanium or titanium alloys containing atleast 30% of titanium, or With tantalum. There may also be used glassvessels or enamelled or rubber-lined vessels. The reaction may also becarried out in brick-lined vessels or, under suitable reactionconditions, in vessels the insides of which are lined with plasticmaterial, for example polyolefins, polytetrafluoroethylene or hardenableunsaturated polyes ers or phenol, cresolor xylenol-formaldehyde resins.As brick-lining there may be used, for example, ceramic material, carbonbricks impregnated with hardenable artificial resins and similar knownmaterials.

The following examples illustrate the invention but they are notintended to limit it thereto:

Example 1 20 liters of ethylene and 10 liters of oxygen are passed perhour by means of two frits at a temperature of C. through a catalystcontaining, per liter of water, 1 gram of PdCl 20 grams oftrichloroacetic acid and grams of CuCl .2l-l The conversion toacetaldehyde, calculated upon the ethylene used, is about 40% after 3days.

The rate of conversion may be kept at this degree, for example byaddition of hydrochloric acid, distilling off acetic acid or the like.Precipitations are not observed even after a prolonged period of time.Acetaldehyde is Washed out and the residual gas is again used in thereaction.

xample 2 The catalyst used was the copper salt of trichloroacetic acidadmixed with 1 gm. PdCl 90 grams of CuC1 .2H O and 1 liter of Water. Theprocedure is the same as that described in Example 1. The conversionfrom ethylene to acetaldehyde is at 45% after one day; this rate ofconversion can be maintained even during a long period of reactionwithout precipitations ocurring, provided that the procedure is the sameas described in Example 1.

Example 3 A catalyst containing the iron salt of trichloroacetic acid isprepared as follows: 8 grams of FeCl are dissolved in water, ammonia isadded, Fe(Ol-I) is filtered off, washed out and then dissolved with asolution containing, per liter of water, 24 grams of trichloroaceticacid, 2 grams of PdCl and 100 grams of CuCl QH O. 20 liters of ethyleneand liters of oxygen are then passed through the catalyst solution at 80C. About 25% of the ethylene used are converted to acetaldehyde. Therate of conversion can be kept at that level for a long period of timewithout precipitations occurring if the process is carried out asdescribed in Example 1.

Example 4 20 grams of trichloroacetic acid are dissolved in 24-5 cc. of0.5 N-sodium hydroxide solution, and 2 grams of Pdcl 100 grams of CuCl.2H O and 755 cc. of water are added. 20 liters of ethylene and litersof oxygen are then passed per hour through the solution at 80 C. Therate of conversion is at 45 provided that the procedure is the same asdescribed in Example 1.

Example 5 The catalyst used is the same as that described in Example 4.Under otherwise identical conditions a mixture of liters of ethylene and5 liters of oxygen, which is outside the limit of inflammability, ispassed through the catalyst solution. The conversion is withoutprecipitations occurring.

I claim:

1. A process for the conversion of an olefinic hydrocarbon to a carbonylcompound selected from the group consisting of aldehydes and ketones byoxidation of an olefinic carbon atom of said olefinic hydrocarbon to acarbonyl group, which process consists essentially of contacting saidolefinic hydrocarbon and oxygen, in a neutral to acid medium with Waterand a catalyst of (a) a salt of a noble metal seiected from the groupconsisting of palladium, iridium, ruthenium, rhodium, and platinum, and(b) as a redox system, copper chloride, said contacting taking place inthe presence of a compound selected from the group consisting oftrichloroacetic acid, dibromoacetic acid, salts of these acids, andmixtures of the aforementioned compounds.

2. A process as in claim 1 wherein said compound selected from the groupconsisting of trichloroacetic acid, dibromoacetic acid, salts of theseacids, and mixtures of the aforementioned compounds is present in anamount of from 1 to 50 percent by weight, calculated as free acid andreferred to the amount of copper present and calculated as CuCl 2H O.

3. A process as in claim 1 wherein said compound selected from the groupconsisting of trichloroacetic acid, dibromoacetic acid, salts of theseacids, and mixtures of the aforementioned compounds is present in anamount of from 20 to 25 percent by weight, calculated as free acid andreferred to the amount of copper present and calculated as CuCl .2H O.

4. A process as in claim 1 wherein said salt of a noble metal is a saltof palladium and in which the ratio of palladium to copper present insaid catalyst is between 25:1 and 500:1.

5. A process as in claim 1 wherein said contacting takes place in thepresence of trichloroacetic acid.

References Cited in the file of this patent UNITED STATES PATENTS1,999,620 Van Peski et al Apr. 30, 1935 2,055,269 Van Peski et al Sept.22, 1936 2,333,216 Trieschmann et al Nov. 2, 1943 2,451,485 Hearne etal. Oct. 19, 1948 2,486,842 Hearne et a1. Nov. 1, 1949 2,690,457Hackmann Sept. 28, 1954 FOREIGN PATENTS 664,879 Germany Apr. 1, 1930713,791 Germany Nov. 14, 1941 891,209 France Mar. 1, 1944 575,571 GreatBritain Feb. 25, 1946 OTHER REFERENCES Phillips: Amer. Chem. Journal,volume 16 (1894), page 267.

Chatt: Chemical Abstracts, volume 48 (1954), pages 50675068.

1. A PROCESS FOR THE CONVERSION OF AN OLEFINIC HYDROCARBON TO A CARBONYLCOMPOUND SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES AND KETONES BYOXIDATION OF AN OLEFINIC CARBON ATOM OF SAID OLEFINIC HYDROCARBON TO ACARBONYL GROUP, WHICH PROCESS CONSISTS ESSENTIALLY OF CONTACTING SAIDOLEFINIC HYDROCARBON AND OXYGEN, IN A NEUTRAL TO ACID MEDIUM WITH WATERAND A CATALYST OF (A) A SALT OF A NOBLE METAL SELECTED FROM THE GROUPCONSISTING OF PALLADIUM, IRIDIUM, RUTHENIUM, RHODIUM, AND PLATINUM, AND(B) AS A REDOX SYSTEM, COPPER CHLORIDE SAID CONTACTING TAKING PLACE INTHE PRESENCE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OFTRICHLORACETIC ACID, DIBROMOACETIC ACID, SALTS OF THESE ACIDS, ANDMIXTURES OF THE AFOREMENTIONED COMPOUNDS.